三年級英語作文：一次有趣的科學實驗

【一】

In ancient times, many people believed the earth was a flat disc. Well over 2,000 years ago; the ancient Greek philosophers were able to put forward two good arguments proving that it was not. Direct observations of heavenly bodies were the basis of both these arguments. First, the Greeks knew that during eclipses of the moon the earth was between the sun and the moon, and they saw that during these eclipses, the earth's shadow on the moon was always round, they realized that this could be true only if the earth was spherical, If the earth was a flat disc, then its shadow during eclipses would not be a perfect circle; it would be stretched out into a long ellipse. The second argument was based on what the Greeks saw during their travels. They noticed that the North Star, or Polaris, appeared lower in the sky when they traveled south, in the more northerly regions, the North Star appeared to them to be much higher in the sky. By the way, it was also from this difference in the apparent position of the North Star that the Greeks first calculated the approximate distance around the circumference of the earth, a figure recorded in ancient documents says 400.000 stadium, that's the plural of the world stadium. Today, it's not known exactly what length one stadium represents, but let's say it was about 200 meters, the length of many athletic stadiums. This would make the Greeks estimate about twice the figure accepted today, a very good estimate for those writing so long before even the first telescope was invented.

【二】

上科學課之前，老師讓我們帶熟雞蛋、太空泥。我一直在納悶，這些到底是幹什麼用的呢?今天謎底終於解開了。

上課了，老師讓我們兩人一組，每組準備一盆水，然後老師說：‘咱們要把浮在水上的東西沉下去，那沉下去的東西浮上來。“我首先把雞蛋放入水中，發現雞蛋是沉下去的，怎麼樣才能把雞蛋浮上來呢?我的問題又來了，不一會，我把雞蛋用手浮到水面上，一鬆手，雞蛋就沉下去了。我不放棄，又想把太空泥裹在雞蛋上會怎麼樣呢?我二話不說，立刻把太空泥裹在雞蛋上，放入水中，雞蛋就浮上來了，我的臉上露出了微笑，心裡想吃了蜜一樣甜。接著，我又把太空泥放入水中，太空泥是浮起來的，我想把一點重物加在太空泥裡，會怎麼樣呢?我開始躍躍欲試，我一邊做，一邊嘴裡說：”先加一點重物，再放入水中。“不一會兒，太空泥就沉下去了，我的實驗又獲得了成功。我高興極了，科學實驗真的太有趣了。